Can kiwifruit combat coeliac disease?

About 60,000 to 70,000 New Zealanders (1.5 per cent) have coeliac disease, a serious autoimmune disease, though most are unaware they have it.

The body produces antibodies to certain peptides naturally produced from the digestion of a protein – gluten – normally present in wheat, oats, rye, and barley.

Those antibodies then cause an inflammatory reaction in the intestines of people who are ‘‘allergic’’ to gluten. Autoimmune diseases are cases of mistaken identity. In coeliac disease, these misdirected attacks permanently damage the lining of the small intestine, reducing its ability to absorb nutrients.

In addition to coeliac disease, about 10 per cent of New Zealanders have a sensitivity to gluten, which may manifest in a range of symptoms, from bloat to itchy skin.

While many go undiagnosed, others self-diagnose gluten intolerance when the problem may lie elsewhere. People with ‘‘allergic-type’’ symptoms often try cutting out dairy and/or gluten, which is a stab in the dark as many allergens have common symptoms and it can be difficult to tease out the source.

Humans have only been eating substantial amounts of wheat and other grains and cereals since the beginning of agriculture, about 10,000 years ago.

Not surprisingly, the disease is prevalent in Europe and countries like New Zealand with diets that feature a lot of bread and cereals that contain gluten. Coeliac disease was recorded as far back as Roman times when it was called sprue.

Gluten is the collective term for a group of proteins in wheat, oats, rye, and barley. These proteins are big – comprising chains of about 250 or more amino acids, the building blocks of proteins.

They can be enormously complex ensembles. The pepsin enzyme in the stomach starts the breakdown of these megamolecules, so that large lumps (on molecular scales) are left. These pass through to the small intestine where, if you have coeliac disease, the trouble starts, usually about three to five hours after eating.

Riddet Institute scientists have been investigating whether natural enzymes in fruits could break down these proteins into smaller fragments that, hopefully, do not stimulate an inflammatory antibody response in the small intestine.

Actinidin, a protein-digesting enzyme naturally present in kiwifruit, looks promising. The idea is to eat some kiwifruit when consuming glutencontaining foods.

Researchers have shown that actinidin can cleave the troublesome gluten into smaller pieces – in the lab.

But further research is required to determine if it will work in the human gut. The institute is testing it using a range of models simulating the human digestive tract.

An important finding from recent Riddet research is that modern food-processing techniques do not cause or aggravate gluten intolerance.

There are already products on the market that aid the digestion of gluten, but kiwifruit could offer a natural alternative with all the added benefits of a whole food containing dietary fibre, vitamin C and other nutrients thrown in.

If investigators prove the kiwifruit enzyme’s efficacy, they will look at how this could work in a balanced diet for coeliac or gluten-intolerant people.

Their hope is to bring relief to the many people worldwide who have to be constantly aware of what’s in their food, which can make eating out tricky and is socially limiting for some.